To make a 1/4- half square, cut two 4-1/4" squares in half
on both diagonals. Sew together two of the resultant quarter square
triangles. Press seam towards darker fabric. To this sew a
half square triangle, cut from a 3-7/8" square. Press towards
the half square triangle. Trim this back to be 3-1/2" if
needed...

To make the pieced rectangles, place a background 3-1/2"
square atop a 3-1/2" x 6-1/2" rectangle, right sides
together. On the back of the square draw in the diagonal and sew on
the drawn line. Cut off the excess seam allowance and press the
remainder towards the darker fabric. Repeat this with another
background square on the other end of the rectangle. Trim these back
to be 3-1/2" x 6-1/2" if needed...Note that some blocks
may need the lines drawn on the squares at opposite
angles!

To make a half squares with half square triangles unit, sew
together two half square triangles cut from 3-7/8" squares. To
the left and bottom of this small half square, sew two more small
half square triangles cut from background 3-7/8" squares. Then
add a larger half square triangle cut from a 6-7/8" square,
pressing seam towards the larger half square triangle. Trim this
back to be 6-1/2" if needed...